Re: [pushed] [gdb/testsuite] Add and use is_x86_64_m64_target

[Pedro Alves <pedro@palves.net>]

On 2023-01-26 5:08 p.m., Tom de Vries via Gdb-patches wrote:
> On 1/26/23 17:38, Pedro Alves wrote:
>> On 2023-01-26 4:10 p.m., Tom Tromey wrote:
>>>>>>>> "Tom" == Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> writes:
>>>
>>> Tom> On 1/26/23 10:17, Tom de Vries wrote:
>>>>> ./gdb.base/jit-reader.exp:
>>>>>    require {is_any_target "i?86-*-*" "x86_64-*-*"} is_lp64_target
>>>>> ./gdb.arch/amd64-i386-address.exp:
>>>>>    require {is_any_target "x86_64-*-*" "i?86-*-*"} is_lp64_target
>>>
>>> Tom> And, doesn't is_lp64_target imply that we're not on an "i?86-*-*" ?
>>>
>>> Tom> Am I missing something here?
>>>
>>> I am not sure.  Can you use 'gcc -m64' on an x86?
>>
>> Yeah, you can.  CodeSourcery toolchains used to be like that back in the day -- 32-bit
>> hosted, so the target triplet indicated 32-bit, but you could use -m64 for 64-bit.
>> No clue what they do nowadays.
> 
> Ah, that's interesting, thanks.
> 
> So, perhaps then you could indeed end up with is_lp64_target == true on an i?86 (by using target board unix/-m64).

Right.

> 
> But assuming you would end up with a complete 64-bit executable, you still wouldn't been able to run it on the 32-bit target, so I think it's a corner-case that doesn't prevent us from dropping the i?86 test here.

Don't know whether that's true on all operating systems.

I may be misremembering -- it may be that gdb was actually built as 64-bit,
but with the toolchain configured to target 32-bit by default (and thus with 32-bit triplet).
In that case, then debugging would work.

See:

  https://sourceware.org/pipermail/gdb-patches/2009-April/064685.html

"x86 -m64" is also why is_amd64_regs_target also runs the test for [istarget "i?86-*"]:

 # Return 1 if target has x86_64 registers - either amd64 or x32.
 # x32 target identifies as x86_64-*-linux*, therefore it cannot be determined
 # just from the target string.
 gdb_caching_proc is_amd64_regs_target {
     if {![istarget "x86_64-*-*"] && ![istarget "i?86-*"]} {
 	return 0
     }

Pedro Alves

> 
> Thanks,
> - Tom
> 
>>
>> Pedro Alves
>>
>>> Or could you have a
>>> 64-bit machine that advertises as i386 if userspace is mostly 32-bit?
>>
>>